I don't pick this feat that often, so I think it's a bit of generalization that it is necessary. I use vigilance elixirs sometimes, on characters that might need it, or just use items to help along. But considering how easily and early invisibility is available, that you can stealth & surprise many encounters yourself, I've found it matters less than I'd expect. You can even go up invisible against the final battle, something that I find weird, since I'd expect certain enemies to just be able to "sense" your presence.
